The ingredients in the different flavors will interact differently with the nic. and other flavors,so different mixes will turn different colors.I've had some start clear and turn yellow,some orange,some will even get very dark,that lemon meringue is a perfect example,that stuff gets so dark,you can't see through it haha.The lite strawberry cheesecake recipe gets a little reddish over time and the lemon meringue pie recipe gets very dark.
Alot of Lorann flavors have food coloring in them though,as they are mainly intended for candy making,so grape is purple,watermelon is pink,etc.